A conventional rotary electronic component will be described below with reference to FIG. 8 through FIG. 13. FIG. 8 is a front view of a rotary encoder as an example of a conventional rotary electronic component. FIG. 9 is an exploded view in perspective of the same, FIG. 10 is a plan view of a stationary substrate, and FIG. 11 is a bottom view of a contact board portion of a rotatable member.
Stationary substrate (hereinafter referred to as substrate) 1 made of a resin is provided, at a flat plane portion 1A thereof, with a plurality of elastic contacts (hereinafter referred to as contacts) 2 made of an elastic sheet metal, each contact constituting a contacting portion as a stationary contact. There is provided, rotatably fitted over the outer periphery of hollow cylindrical wall 1B disposed in the center, cylindrical shaft 3A of rotatable member 3 made of an insulating resin. In the circumference of rotatable member 3, there is provided flange-shaped contact board portion (hereinafter referred to as board portion) 3B. On to the underside of board portion 3B, there is fixed, by insert-molding, metallic annular contact (hereinafter referred to as contact) 4. Contact 4 serves as a movable contact. Further, leg portion 6A of cover 6 covering over the top face of board portion 3B is bent at its end so that each contact 2 on substrate 1 is adopted to make contact with contact 4. By virtue of the described configuration, rotatable member 3 in its entirety is positioned with respect to substrate 1.
FIG. 12 is a plan view showing a state of a metallic contact plate before being subjected to assembly work. As shown in FIG. 12, contact 4 has predetermined signaling contact portions (hereinafter referred to as contact portions) 4B disposed at spaced positions in electrical continuation with ring portion 4A, which is continuous all around its circumference. Before being subjected to assembling work, contact 4 is fixed to frame portion 5B by connection supports 5A, which collectively form metallic contact plate 5. When rotatable member 3 is subjected to molding work, metallic contact plate 5 is fixed on to board portion 3B by insert-molded with an insulating resin. Thereafter, connection supports 5A are cut off and thereby board portion 3B is formed in the circumference of rotatable member 3.
By rotating rotatable member 3 by way of cylindrical shaft 3A, contacting portions 2A and 2B of contact 2 are allowed to slide on ring portion 4A and contact portion 4B of contact 4, respectively. Thereby, electric signals repeating OFF-ON state in accordance with a predetermined rule as shown in FIG. 13 are generated and the signals are output to a circuit of an electronic apparatus used, through a predetermined outputs 8.
Further, as shown in FIG. 8, the conventional rotary electronic component has push switch 7 in the center of cylindrical wall 1B on substrate 1. By pushing this push button 7A, push switch 7 can be actuated independently of the above described rotary encoder portion.
Such a rotary electronic component is disclosed for example in Japanese Patent Non-examined Publication No. H11-176287.
Rotary electronic components of the described type are given a relatively large bore such that another independent electronic component such as push switch 7 is accommodated therein as noted above. For use in an electronic apparatus, it is required that the generated electronic signal be stable for a long time. To meet such requirement, it is necessary that the contact portions responsible for generating the electric signal be formed to be stable.
However, in a conventional rotary encoder as a conventional rotary electronic component, as noted above, contact 4 as movable contact is formed by insert-molding metallic contact plate 5, with an insulating resin, so as to be fixed on to rotatable member 3. Therefore, when board portion 3B of a large-bored rotatable member 3 is processed by such molding, a considerably great amount of shrinkage occurs in the insulating resin while it is cooled and hardened. On the other hand, metallic contact plate 5 insert-molded and fixed on to board portion 3B scarcely shrinks under the changes in temperature. Further, contact 4 has circular ring portion 4A continuous around the entire circumference, it hardly deforms. Therefore, a stress due to shrinkage of the insulating resin is induced at board portion 3B. In the extreme, contact 4 will partly rise or board portion 3B will warp. Hence, fluctuations of the electric signal may sometimes be caused during the use for a long time.